Gang condenser and method of adjusting same



Nov. 27, 1928. 1,693,286

E s PRIDHAM ET AL GANG CONDENSER AND METHOD OF ADJUSTING SAME Filed March 17, 1926 2 Sheets-Sheet 1 1N VEN TORS. E0 W//v s. PR/DHAM.

DONALD K. L/PP/NC'OTT M7, flwf/MRf? E. S. PRIDHAM ET AL GANG CONDENSER AND METHOD OF ADJUSTING SAME Nov. 27, 1928.

Filed March 17, 1926 2 Sheets-Sheet 2 INVENTORS. 50W/N s. PR/DHAM.

'DONALD l( L/PP/NCOTT.

f@ A TTOR YS.

Patented Nov. 27, 1928.

vUNITED STATES PATENT OFFICE.

EDWIN S. PRIDHAM, OF OAKLAND, AND DONALD K. LIPPINCOTT, OF ALAMEDA, CALI- FORNIA, ASSIGNORS T0 THE MAGNAVOX COMPANY, OF OAKLAND, CALIFORNIA, A

CORPORATION OF ARIZONA.

GANG CONDENSER AND METHOD OF ADJUSTING SAME.

Application led March 17, 1926; Serial No. 95,169.

This invention relates to variable condensers for use in radio and other frequency work.

In order to simplify the tuning of a receiving set it is desirable to mount a number of condensers on a single shaft so that they may be moved simultaneously with a sinfrle control. It is essential to the successful operation of such gang condensers that the capacities of the units be equal at thevarious positions of the rotor. The object of the ang igh present invention is to facilitate adjustment of the units during assembly to insure equal capacities. For this purpose we so mount the stator units in a frame that individually they may be conveniently shifted laterally in either direction and at either end. Each unit of the gang condenser is then connected in turn in an oscillating circuit wherein the tuning coil associated with the condenser forms the inductance and the condenser unit forms the capacity. This oscillating circuit may then be used as a standard and each unit brought into resonancetherewith in all positions of the rotor, by laterally shifting the stators. Once the proper adjustment of the stators is obtained they can be permanently fixed.

One form which our invention may assume is exemplified in the following description and illustrated in the accompanying drawings, in which Fig. 1 shows a perspective view of the condenser;

Fig. 2 shows a plan viewof the same;

Fig. 3 shows a sectional view taken on the line 3-3 of Fig. 2;

Fig. 4 shows a similar view of the con denser with the rotor in open position;

Fig. 5 shows an end view of the stator, illustrating the shiftable connection between the end of the stator and the frame;

, Fig. 6 shows a pers ective view of the adjusting wrench used or shifting the stator.

Referring in detail to the accompanying drawing, the condenser therein illustrated comprises a rectangular frame 10 within which. a plurality of stators are mounted, there being three stators in the present device. Each stator com rises spaced plates 11 soldered at their en s to cross-plates 12.

y AEach cross-plate has a shifting bar 13 arranged on its inner face vand carrying a`pair of bolts 14 which extend through slots 15 in the cross-plates and thence through openings in the frame 10. There is a keyway 16 in each crossplate, arranged in juxtaposition with an opening or socket 17 in the frame.` A wrench 18, as shown in Fig. 6, is inserted in the opening or socket 17 and has an eccentric pin 19 to engage in the keyway 16 for the purpose of shifting the stators laterally in either direction before the bolts 14 are tightened.

Between the stators we arrange shield plates 20, which are provided with ground connections 21. These plates are also shiftable laterally and serve to vary the minimum capacity of the condenser units.

The rotors of the condenser are mounted upon a shaft 22 journaled in the frame. Each rotor consists of spaced plates 23 soldered to a sleeve or barrel 24. The sleeve is fitted over the shaft 22 and locked in place thereon by screws 25'passing through hubs 26 on either end of the sleeve. The sleeve serves to space the plates apart, and

they are additionally spaced\\and reinforced and soldered to thev cross-plates 12. The

stator sections are next loosely mounted in the frame.- The rotor sections are likewise arranged in a jig and soldered to the brass sleeves 24, and the end lugs likewise soldered together. The rotors are then mounted on the shaft 22 and fastened thereto in parallel relation by means of a jig or gauge.

At this time we connect in turn each unit of the gang condenser in an oscillating circuit, the tuning coil of the particular set forming the inductance and the unit condenser of the gang forming the capacity. We now choose a standard frequency for comparison purposes. Adjustment of the stator of the test condenser is then made until the frequency of the test circuit is equal to the frequency of the Standard cir- In like manner the capacities of the that the respective frequencies of the circuits of which they form a part are equal to the chosen standard.

A new standard frequency is then chosen, such that if the first standard frequency chosen should utilize the maximum capacity of the test condenser, then the new standard is chosen so as to use about one-half the capacity of the test condenser. Adjustments of the stators are again made so that the frequency in each circuit is made equal to the new standard frequency. This result must of course be obtained without upsetting the previously equalized capacities.

As many standard frequencies may` be used as desired, and for each standard the several units are made equal to each other bty being made equal to the standard. Thus, i at a number of points on the dial the capacities are equal, it is a safe assumption that from maximum to minimum the capacities of the various units are equalized.

The work of equalizing the test circuits with the standard is made easy by the fact that if the two circuits are not in perfect resonance a heterodyne note is heard in a detector circuit; adjustment is then made until this note disappears; and then it is known that the two. circuits are in perfect resonance.

There are other methods of determining when the two circuits are in perfect resonance, as, for instance, measuring the peak of current with a meter; but the heterodyne method lends itself so well to large produc` tion that it is the preferred method.

Should there be any heterodyne beat in the circuit when the rotor sections are at zero, then the minimum capacity of the condenser can be adjusted by varying the position of the adjacent shield plates 20. When all of the condensers are at equal capacities the bolts 14 are tightened and permanently secured.

In and by the present invention we are enabled to readily and easily equalize, the capacities of a gang condenser during assembly and set them permanently in position within the frame, thus obviating the necessity for any individual adjustment or tuning thereafter. By thus accurately balancing and equalizing the capacities ofthe several condensers, a unit control may be employed with entire satisfaction.

Various changes in the construction and arrangement of the several parts herein shown may be employed without departing from the spirit of our invention as disclose in the appended claims.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

l. In a condenser, a plurality of stators, each formed of spaced plates, a cross-plate at each end of each stator section, a shiftable bar carried by each cross-plate, bolts connected to the shiftable bar and extending through slots in the cross-plate, a frame for the stator sections having openings through which said bolts extend, and means insertable through the frame to engage the crossplates for shifting the same laterally to permit A adjustment during assembly.

2. In a condenser, a plurality of stators, each formed of spaced plates, a cross plate at each end of each stator section and having a lurality of elon ated slots therein, a shiftalile bar carried y each cross late, bolts connected to the shiftable bar and) extending through a pair ofthe slots in the cross plate, a frame for the stator sections having openings through which the bolts extend, and

means insertable through the frame and having engagement with the other of said elongated slots in the cross plate for shifting the same laterally to permit adjustment of the stators during assembly.

EDWIN S. PRIDI-IAM. DONALD K. LIPPINCOTT, 

